IMT-Advanced 4G Wireless Communication Networks
International Mobile Telecommunications (IMT)-advanced networks are the latest effort in International Telecommunication Union (ITU)-R for 4G wireless communications. One goal is to provide an uplink peak spectrum efficiency of 15 bits per second (bps) per Hz, and throughput as high as possible in the edge area of a network cell, given a reasonable network complexity. To achieve this goal, various enabling technologies have been described. A current consensus is to use relay stations (RS) for the improvement of link performance.
The IEEE802.16j standard has also adopted RS. This invention is particularly related to the uplink of 4G wireless communication networks where the RS is used.
Relay and Network Encoding
Relay-based communications facilitates the cooperative decoding at a receiver to improve an overall link performance. There are in general two types of relay-based communication: amplifying and forwarding (AF) and decoding and forwarding (DF). The invention uses the DF. In network encoding, the network is modeled as a graph, where edges represent channels from a transmitter to a receiver. Using the max-flow min-cut theorem, it is possible to calculate the maximum amount of information flow that can be transmitted from a source to a specific receiver. Network coding can enable all intended receivers to get the maximum network information flow from the source simultaneously. Network encoding and channel coding both use operations in finite fields.
Cooperative Communications
One purpose of cooperative communication is to provide multiple links or channels for the communication between a source and destination node so that a virtual multiple-input multiple-out (MIMO) communications is provided for encoding and diversity.
Turbo Decoding of Network Encoding and Channel Encoding
In wireless communications, the data transmitted from the source to the destination are usually channel encoded to reduce the effect of channel noise. Channel encoding uses a forward error correction (FEC) code, and often with bit interleaving. The channel code is used to protect the transmitted data in the presence of noise. After data from one source node is received at the destination, the decoding of the received data to recover the source information can be carried out independent of the decoding of data from other source nodes. In the case of network coding, because all data are network encoded at the RS, decoded information of current data can be used to improve the decoding of other data. As a result, a turbo decoding process can be built up so that the decoding alternates between the channel decoding (single-user decoders) and network decoding (multi-user decoder).